Method of making jet fuel and use thereof



- hot spots in the combustor.

3,077,733 Fatented Feb. 19, 1963 3,077,733 METHOD F MAKENG JET FUEL ANDUSE THEREOF William N. Axe and Dean P. Montgomery, Bartlesville,

0kla., assiguors to Phillips Petroleum Company, a corporation ofDelaware No Drawing. Filed Aug. 17, 1959, Ser. No. 833,974

4 Claims. (Cl. 60-35A) desulfur-ization step, the product contains someunsaturated materials together with the saturated materials.

.tFuels produced in this manner range from about 85 per- ;cent to about93 percent saturated. While these fuels yield certain advantages overaliphatic hydrocarbon turbojet fuels, actual tests have demonstratedthat considerable difiiculties are presentwhen such fuels are utilized.In particular, coke deposits occur in the combustor chamber, theafterburner, and the tail pipe, and particularly at the combustornozzle. The skin temperature at local- :ized regions'within thecombustion chamber may become undesirably or even dangerously high. Animportant :contributionto such excessive temperatures is made by;-undesirable luminosity of the flame from the fuel com- .bustion. Suchluminosity causes radiation of heat to the metal and other parts of theengine.

. In accordance with this invention, a hydrodesulfurized highly.aromatic feedstock is hydrogenated to provide a and the luminosity ofthe flame is reduced to acceptable levels, thereby preventing theoccurrence of undesirable Surprisingly, these advantages result in asubstantial improvement in performance despite the fact that thehydrogenation reduces the volumetric heat content of the fuel, i.e., itsdensity, a result considered highly undesirable by previous workers.

Where heavy cycle oil is used as a feedstock, a satura- 'tion' of 95percent or higher cannot be attained without virtually complete removalof sulfur prior to the hydrogenation step.

The hydrodesulfurization can advantageously be accomplished with the aidof a cobalt molybdate catalyst or,

under high hydrogen pressure and elevated temperatures,

' by treatment 'witha stoichiometric quantity of sodium.

After the hydrodesulfurization treatment, the highly aromatic stock canbe readily hydrogenated until it is 95 percent or more saturated.

In the operation of turbojet engines with the present fuel, air is fedthrough an air compressor to the combustion chamber of the engine, whichis formed from refractory metals or alloys designated to withstandspecific combustion temperatures.

In this chamber, the fuel and air are mixed, and the mixture is ignited.

The resulting burned mixture is diluted with secondary air in anafterburner and expanded through a turbine which drives an aircompressor. Thereupon, the gases are ejected through a jet or tail pipeinto the atmosphere with In turboprop engines, the principle ofoperation is essentially the same except that the majority of the energyis expended in driving the turbine which, in turn, is connected to apropeller.

Due to the large number of intricately shaped vanes in the turbine, itis evident that coke deposits are a very serious problem, as are suchdeposits in the combustion chamber or nozzle. Moreover, if the designtemperature at localized regions Within the engine is exceeded, it isevident that serious damage to the engine can result, or

even a catastrophic failure.

The feedstocks utilized in the process of this invention are aromaticfractions built up during the catalytic cracking of gas oil. They arederived by extraction,

'usually with sulfur dioxide or furfural, of catalytic cracker cycleoil. The aromatic extract boils within the range of 450 to 1,000 F. atatmospheric pressure. It is characterized by a sulfur content of 0.25 to2.5 weight percent, a nitrogen content of .03 to .3 Weight percent andan oxygen content of 0.25 to 2.5 weight percent. The oil is at least 50volume percent aromatic as determined by molybdate, molybdenum oxide.molybdenum sulfide, tungsten sulfide or other known hydrodesulfurizationcatalysts. As those skilled in the art will understand, thehydrodesulfurization is effective to remove oxygen andnitrogencontaining compounds as well as the sulfur compounds. In oneaspect of the invention, the sulfur is removed by treatment with astoichiometric quantity of sodium (based on sodium sulfide formation)under high hydrogen pressure and elevated temperatures. The quantity ofhydrogen utilized in the hydrodesulfurization must be at least thestoichiometric equivalent of the quantity of sulfur, nitrogen, andoxygen present in the feed to the hydrodesulfurization step plus thequantity required to replace the sulfur, nitrogen and oxygen. To insurecomplete removal of these materials, the hydrogen should be at least 150percent of the theoretical quantity required.

In order that the fuel may have a final saturation of at least percentin accordance with the invention, it is essential that virtuallycomplete removal of the sulfur, nitrogen and oxygen compounds beeffected. In particular, the sulfur content of the hydrodesulfurizedmaterial should be less than 0.05 percent, the nitrogen content shouldbe below 0.05 percent, and the oxygen content should be below 0.1percent.

The conditions of temperature and pressure for thehydrodesulfurizationstepare well known to those skilled in the art andform no part of this invention. Suitable conditions are a total pressureof 1,000 pounds per square inch and a temperature of 750 F.

The material is then hydrogenated to provide a fuel which is 95 topercent saturated. To this end, catalytic hydrogenation with a nickel,platinum or other known hydrogenation catalyst is suitable. Suitablehydrogenation conditions are Well known to those skilled in the art. Ingeneral, the amount of hydrogen utilized ranges from 2500 to 5000 cubicfeet per barrel hydrogenated. A pres-sure of at least 1,000 pounds persquare inch or higher is suitable, and temperatures may range from 400to 600 F.

AT TestFtiel-AT TetralinX 100 AT Isooctane- AT Tetralin This is not alinear measurement, and luminometer readings ofless than 30 have beenfound to give rise to unsatisfactory operating conditions, particularlythe production of localized hot spots, in the operation of jet engines.It is surprising that'the fuel of this invention realizes the foregoingadvantages and yet maintains a high net heat of combustion in-excess of130,000 B.t.u. per gallon, the heatof vaporization of the water-ofcombustion being excluded fromthis figure. Moreover, the jet. fuels ofthe invention have low pour points below "-10" F., for example, -35 F.The density ranges between-;850 and 1.000 gram per cubic centimetermeasured at 20 C.

his a feature of the invention that 'a practically quantitative removalof unsaturation can be effected by treating the hydrogenated materialwith silica gel. This results in'ev'en'greater advantages, particularlyas regards coke disposition and production of hot spots. In particular,by'this final treatment, materials having a saturation "of 99.5percentormore can be obtained. Instead of utilizing silica gel, thefinal treatment may be efiected by 'treatment'with sulfuric acid andwater-washing the thus "treated material.

SPECI-FIC EXAMPLE In one' specific run, the novel jet fuel compositionof "the invention was made from a sulfur dioxide extract "of a cycle oilfrom a catalytic cracking operation. The

oil had the following characteristics.

Luminosity- Bureau of Mines correlation index 92.

Volume percent non-aromatic material 24.8.

Two percent of the material was distilled at 518 F. an'd'95 percent ofthe material was distilled at 890 F. at atmospheric pressure.

' This oil was solvent extracted with dimethylsulfoxide :at 180 F. and asolvent/oil ratio of 3/1. The extract yield was about 75 volume'percentof the charge and had a" gravity of 2.7 API (density of 1.054 g./cc.).The 'extra ctwas about 5 volume percent non-aromatics.

/ The extract from the preceding step Was treated by passing it twiceover a cobalt molybdate catalyst which was supported on alumina. Thecomposition corresponded 'to 3 percent cobalt -oxide and 7.5 percentmolybdenum oxide. The treatment took place at apressure of 500 poundsper square inch, a temperature of 800 F., and a liquid hourly spacevelocity of 1, the amount of hydro- "gen supplied being 1,000 cubic feetper barrel of feed.

'1 After this treatment, a small amount of material boiling v at lessthan 400 F. was separated'by fractional distillation from the remainderof the product.

Upon analysis of the product after the described hydrodesulfurizationtreatment, the amount of sulfur, oxygen "and nitrogen present was toohigh to attain the desired 5 oxide and 6.6 percent molybdenum trioxide.

extent of hydrogenauon. Accordingly, the material was subjected toanother hydrodesulfurization treatmentntilizing a cobalt molybdatecatalyst supported on alumina, the composition of which corresponded to4.2% cobalt The conditions used in this step were a temperature of 775F., and a liquid hourly space velocity of 0.5, the amount of hydrogensupplied being 4,000 cubic feet per barrel of feed. The total treatmenttime was 6hours. After 10 this treatment, the sulfur content was 0.05%,and the amount of oxygen and nitrogen originally present had beencorrespondingly reduced.

The product from the aforementioned hydrodesulfurization steps wasfractionated, and 4.9 Weight percent ofthe material, which had a boilingpoint of less than 400 F., was separated from the rest of the product.About 320 parts of the material boiling above 400 F. was placed in arocking autoclave and 74parts of a reduced nickel "on' kieselguhrhydrogenation catalyst was added.

ZO'Hydrog'en-Was added periodically at a temperature of I 500 Fiuntilnofurther addition of hydrogentookplace "ata total pressureof 1500pounds. The hydrogenated product had a density of 0.909 'gram' per cubiccentimeter at 2 0 C.,' a carbon -to hydrogen ratio of 87.2:13.0, a

"r'efractive index of 1.4907 at 21 C.,- and a viscosity of 50.56-centistokes at 100 F. or 33.00 at-21'0" F. The product hada'gr'oss heat'of c'ombustion of 148,000 B.t.u. per gallon which oorrespo'nzlsapproximately to'a net value of about 140,000. i The pour'point"was-3S--'F.

3O Thehydrogen consumption during-the hydrogenation step FractionBolling Point Volume V Percent Less than 400 F Y "4.5 400 to 500 F 13.8500 to 600 F" 40.6 Over 600 F"..- 41. 1

FRACTIONS DISTILL ED FROM FRACTIONt 5 600 to 700 F -28. 8 6 Over 700 F12.3

II- raction 3 had a net heat of cornbustion'of 137,000

' B.t.u. per gallon, a molecular Weight of 213 determined by thefreezing point depression method in benzene, a --density "of-0.9037 gramper cubic-centimeter at 20 C., "a viscosity of 5.5 centistokes at 100C., and a viscosity of 1.70 centistokes at 210 C.

Fraction 4 had an atomic ratio of carbon to hydrogen of 88.3:12.0, a netheat of combustion of 18,247 B.t.u. per pound,.a molecular weight of 263determined by the freezing point depression method in benzene, a densityof 0.9367 gram per cubic centimeter at 20 C., a viscosityofi43centistokes at 210 C., and-a'luminometer reading of 38.5.

Fraction '5 hada density -of 0.9297 gram per cubic centimeter at 20C.Fraction 6 had a density of 0.9683 gram per cubic'centimeter at 20 C.and a net heat of combustion of'145,200'B.t.u. per gallon.

W-hen tested as a jet fuel, after a long periodof operation withfraction 3, the engine is much freer from carbon deposits than is thecase wherein the engine is operated with a hydrogenated aromaticfraction whichis 92-93 percent saturated. Due to the'improved degree-ofWhile the invention has been described inconnection with a preferredembodiment thereof, it is understood that variations in materials andconditions may be made without departing from the spirit and scope ofthe invention.

We claim:

1. The method of making a jet fuel, which comprises extracting cycle oilfrom a catalytic cracking operation with sulfur dioxide, extracting aresulting aromatic fraction extract with dimethylsulfoxide,hydrodesulfurizing the resulting aromatic fraction extract having asulfur content of 0.25 to 2.5 weight percent in the presence of cobaltmolybdate to reduce said sulfur content to less than 0.05 weightpercent, and hydrogenating the resulting material until it is 95 to 100weight percent saturated.

2. The method of making a jet fuel, which comprises extracting cycle oilfrom a catalytic cracking operation with a solvent selected from thegroup consisting of sulfur dioxide and furfural, extracting theresulting aromatic fraction extract with dimethylsulfoxide, theresulting aromatic fraction extract boiling within the range of 450 to1000 F. at atmospheric pressure and having a sulfur content of 0.25 to2.5 weight percent, hydrodesulfurizing the latter aromatic fractionextract with hydrogen in the presence of a hydrodesulfurizing catalystselected from the group consisting of cobalt molybdate, molybdenumoxide, molybdenum sulfide, and tungsten sulfide to reduce the sulfurcontent to less than 0.05 weight percent, the nitrogen content to below0.25 weight percent and the oxygen content to below 0.1 weight percent,and hydrogenating the resulting material in the presence of ahydrogenation catalyst to provide a fuel which is 95 to 100 weightpercent saturated and has a ltuninometer of at least 30.

3. The method of making a jet fuel, which comprises extracting cycle oilfrom a catalytic cracking operation with sulfur dioxide, extracting theresulting aromatic fraction extract with dimethylsulfoxide to provide anaromatic fraction extract boiling within the range of 450 to 1000 F. atatmospheric pressure and having a sulfur content of 0.25 to 2.5 weightpercent, a nitrogen content of 0.03 to 0.3 weight percent and an oxygencontent of 0.25 to 2.5 weight percent, hydrodesulfurizing the latteraromatic fraction extract with hydrogen in the presence of cobaltmolybdate to reduce the sulfur content to less than 0.05 weight percent,the nitrogen content to below 0.05 weight percent and the oxygen contentto below 0.1

Weight percent, hydrogenating the resulting material in the presence ofa catalyst comprising nickel to provide a hydrogenated product which isto weight percent saturated and has a luminorneter value of at least 30,treating the said hydrogenated product with a compound capable ofabsorbing aromatic material to provide a material which is 99 to 100weight percent saturated, and fractionating the thus treated material toprovide a fuel having a preselected boiling range for jet engineoperation.

4. The method of operating a jet engine, which comprises mixing fuel andair in a combustion chamber, causing combustion of said fuel and air,and ejecting the combustion gases through a nozzle to produce apropulsive thrust, said fuel being prepared by extracting cycle oil froma catalytic cracking operation with a solvent selected from the groupconsisting of sulfur dioxide and furfural, extracting the resultingaromatic fraction extract with dimethylsulfoxide, the resulting aromaticfraction extract boiling within the range of 450 to 10 00" F. atatmospheric pressure and having a sulfur content of 0.25 to 2.5 weightpercent, a nitrogen content of 0.03 to 0.3 weight percent, and an oxygencontent of 0.25 to 2.5 weight percent, hydrodesulfurizing the latteraromatic fraction extract with hydrogen in the presence of ahydrodesulfurizing catalyst selected from the group consisting of cobaltmolybdate, molybdenum oxide, molybdenum sulfide, and tungsten sulfide toreduce the sulfur content to less than 0.05 weight percent, the nitrogencontent to below 0.05 weight percent and the oxygen content to below 0.1weight percent, and hydrogenating the resulting material in the presenceof a hydrogenation catalyst to provide a fuel which is 95 to 100 weightpercent saturated and has a luminometer of at least 30.

References Cited in the file of this patent UNITED STATES PATENTS1,276,219 Holmes Aug. 20, 1918 1,908,286 Dorrer May 9, 1933 2,385,981Friedman Oct. 2, 1945 2,671,754 De Rossett et al Mar. 9, 1954 2,737,538Nelson Mar. 6, 1956 2,768,986 Johnson et al Nov. 26, 1956 2,769,753Hutchings et a1. Nov. 6, 1956 2,769,754 Sweetser et a1. Nov. 6, 1956

1. THE METHOD OF MAKING A JET FUEL, WHICH COMPRISES EXTRACTING CYCLE OILFROM A CATALYTIC CRACKING OPERATION WITH SULFUR DIOXIDE, EXTRACTING ARESULTING AROMATIC FRACTION EXTRACT WITH DIMETHYLSULFOXIDE,HYDRODESULFURIZING THE RESULTING AROMATIC FRACTION EXTRACT HAVING ASULFUR CONTENT OF 0.25 TO 2.5 WEIGHT PERCENT IN THE PRESENCE OF COBALTMOLYBDATE TO REDUCE SAID SULFUR CONTENT TO LESS THAN 0.05 WEIGHTPERCENT, AND HYDROGENATING THE RESULTING MATERIAL UNTIL IT IS 95 TO 100WEIGHT PERCENT SATURATED.
 4. THE METHOD OF OPERATING A JET ENGINE, WHICHCOMPRISES MIXING FUEL AND AIR IN A COMBUSTION CHAMBER, CAUSINGCOMBUSTION OF SAID FUEL AND AIR, AND EJECTING THE COMBUSTION GASESTHROUGH A NOZZLE TO PRODUCE A PROPULSIVE THRUST, SAUD FUEL BEINGPREPARED BY EXTRACTING CYCLE OIL FROM A CATALYTIC CRACKING OPERATIONWITH A SOLVENT SELECTED FROM THE GROUP CONSISTING OF SULFUR DIOXIDE ANDFURFURAL, EXTRACTING THE RESULTING AROMATIC FRACTION EXTRACT WITHDIMETHYLSOLFOXIDE, THE RESULTING AROMATIC FRACTION EXTRACT BOILINGWITHIN THE RANGE OF 450 TO 1000* F. AT ATMOSPHERIC PRESSURE AND HAVING ASULFUR CONTENT OF 0.25 TO 2.5 WEIGHT PERCENT, A NITROGEN CONTENT OF 0.03TO 0.3 WEIGHT PERCENT, AND AN OXYGEN CONTENT OF 0.25 TO 2.5 WEIGHTPERCENT, HYDRODESULFURIZING THE LATTER AROMATIC FRACTION EXTRACT WITHHYDROGEN IN THE PRESENT, A NITROGEN CONTENT OF SULFURIZING CATALYSTSELCTED FROM THE GROUP CONSISTING OF COBALT MOLYBDATE, MOLYBDENUM OXIDE,MOLYBDENUM SULFIDE, AND TUNGSTEN SULFIDE TO REDUCE THE SULFUR CONTENT TOLESS THAN 0.05 WEIGHT PERCENT AND THE OXYGEN CONTENT TO BELOW 0.05WEIGHT PERCENT AND THE OXYGEN CONTENT TO BELOW 0.1 WEIGHT PERCENT, ANDHYDROGENATING THE RESULTING MATERIAL IN THE PRESENCE OF A HYDROGENATIONCATALYST TO PROVIDE A FUEL WHICH IS 95 TO 100 WEIGHT PERCENT SATURATEDAND HAS A LUMINOMETER OF AT LEAST 30.